Is a Colt 7.62x39 mag just a regular 5.56 20-rd mag?

[IMtheNRA]

I ended up with a Colt magazine that has a base plate marked 7.62x39. If the mag was ever blocked to five rounds, the block is now long gone.

The magazine appears to be exactly the same as my standard Colt 5.56 20-round mags.

Can I just toss this mag in with my 5.56 magazines, or is there some subtle difference that I can't see?

 

[Scooter22]

I don't know about AR mags but other rifles I've used, the followers have a slightly different profile.

 

[rcmodel]

Yes, they can't be the same, and work right.
If not the body, which would surprise me greatly.
At least the follower has to be different.

rc

 

[gunnutery]

Your question reminded me of this video: http://www.youtube.com/watch?v=i160RyAB2ow

I thought there was a second video explaining what he did to the internals but I can't seem to find it. The link to ar15.com may explain it in more detail, (sorry, didn't re-read through it thoroughly right now).
http://www.ar15.com/forums/t_3_17/557754_Longziz__2__The_only_Universal_AR15_Magazine.html

Basically Longziz came up with a 2 follower system inside a standard ar15 magazine. IIRC the top follower is completely free to tilt and allows the x39 to load and feed correctly. I haven't heard anything more out of Longziz, even though he came out with some really intriguing designs.

 

[Tirod]

The magazine appears to be exactly the same as my standard Colt 5.56 20-round mags.

That suggests it's a x39 base plate on a 5.56 mag. Furthermore, the two major ribs at the cartridge nose would be too restrictive for the wider stack dimension of x39.

Load it up and see.

Pics would be nice.